# Plasmonic Hot‐Carrier Redox Enables Proton‐Coupled Electron Transfer at C─H Bonds

## TL;DR

This paper shows how plasmonic materials can control electron and proton transfer to activate strong C-H bonds using visible light.

## Contribution

The study introduces plasmonic photocatalysis as a new platform for probing PCET mechanisms with precise control.

## Key findings

- Plasmonic photocatalysis enables oxidative C-H bond activation via a stepwise electron-then-proton transfer pathway.
- The average plasmonic oxidation potential is estimated at ∼0.64 V versus Fc⁺/Fc.
- Plasmonic materials are shown to be both efficient light absorbers and mechanistic probes for PCET.

## Abstract

Proton‐coupled electron transfer (PCET) enables the activation of strong X─H bonds (X = C, N, O) under mild conditions, yet mechanistic interrogation remains challenging due to limited control over electron and proton energetics. Here, we demonstrate that plasmon‐driven photocatalysis provides a powerful platform to disentangle these contributions. Using gold nanoparticles supported on an engineered energy‐filter substrate as photoelectrodes, we achieve oxidative C─H bond activation in 1‐benzyl‐1,4‐dihydronicotinamide via multi‐site PCET under visible‐light excitation. Photocurrent kinetics and energetics zone analysis reveal an electron‐then‐proton transfer (ET–PT) pathway that requires pre‐association of the base. The average plasmonic oxidation potential is estimated at ∼0.64 V versus Fc⁺/Fc, corresponding to hot‐hole energies of ∼0.52 eV. These findings establish plasmonic materials not only as versatile light absorbers for photoredox catalysis but also as mechanistic probes for resolving fundamental PCET pathways.

Plasmonic hot carriers provide unprecedented control over coupled electron–proton transfer, enabling visible‐light activation of strong C─H bonds. Using an energy‐filter electrode, we reveal a stepwise electron‐then‐proton pathway and directly tune the underlying driving forces. This work positions plasmonic nanostructures as a powerful new platform for uncovering fundamental reaction mechanisms.